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4.1 Medical Microbiology > URTIs - laryngitis, CROUP, epiglotitis, Whopping Cough, Sinusitis, Otitis > Flashcards

URTIs - laryngitis, CROUP, epiglotitis, Whopping Cough, Sinusitis, Otitis Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

What is laryngitis?

A

Inflammation of the larynx/vocal cords -> causes one to loose their voice

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2
Q

Write a note on the aetiology of laryngitis
(4)

A

Acute laryngitis is usually viral in nature

Bacterial laryngitis is extremely rare

Fungal laryngitis is only seen in immunocompromised

Laryngitis can be seen during the course of or after another illness e.g. nasopharyngitis

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3
Q

What viruses cause laryngitis?
(6)

A

Parainfluenzae virus
Influenza virus
Respiratory syncytial virus
Rhinovirus
Coronavirus
Echovirus

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4
Q

What are some bacteria responsible for the rare cases of bacterial larngitis?

A

S. pyogenes
M. catarrhalis
C. diptheria
M. tuberculosis (lecturer has never seen this but it can happen)

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5
Q

What is the medical term for Croup?

A

Laryngotracheitis

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6
Q

What happens in Croup?
(4)

A

InfIammation of the laryngotrachea (wind pipe)

Wind pipe begins to close in one area -> bottle shaped wind pipe

Children and babies find it hard to catch their breath/breathe in

Lasts 5 to 6 days

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7
Q

Talk about the aetiology of Croup
(4)

A

Caused by viruses or bacteria

Bacteria cause more serious infections

Can be caused by unusual bacteria

Severity ranges from a baby coughin at night to being rushed to hospital as an emergency

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8
Q

What viruses cause croup?
(5)

A

parainfluenza viruses
Respiratory syncytial virus
Adenoviruses
Influenza viruses
Enteroviruses

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9
Q

What viruses cause croup?
(5)

A

parainfluenza viruses
Respiratory syncytial virus
Adenoviruses
Influenza viruses
Enteroviruses

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10
Q

What bacteria cause Croup?

A

H influenza type B
S pyogenes
S aureus
C diptheria
Mycoplasma pneumonia

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11
Q

What bacteria cause Croup?

A

H influenza type B
S pyogenes
S aureus
C diptheria
Mycoplasma pneumonia

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12
Q

Talk about the epidemiology of croup
(3)

A

Children under 5 are more likely to have croup -> its said that every child before 5 has had croup at some point

Premature babies are at a much higher risk

More common during winter months and early spring (viral)

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13
Q

What is acute epiglottitis?

A

Inflammation of the epiglottis

Swelling leads to blockage of the airway which can be life-threatening - patient will usually require an emergency tracheostomy

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14
Q

What causes epiglottis?

A

Encapsulated strains of H.influenzae type b

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15
Q

Talk about the epidemiology of epiglottitis
(3)

A

Only really caused by Hib and since introduction of Hib vaccine cases are now very rare

Only 11 cases between 2004 and 2011

Historically more common in children but its now a disease in adults due to waning immunity

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16
Q

How is epiglottitis diagnosed?

A

Throat examination
Neck Xray
Throat culture and blood tests to detect Hib

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17
Q

How is epiglottitis treated?

A

Prompt antimicrobial treatment

Cefotaxime or chloramphenicol

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18
Q

What is whopping cough medically known as?

A

Pertussis

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19
Q

What is whopping cough/pertussis?
(5)

A

Infection of the ciliated bronchial epithelial cells

Caused by Bordetella pertussis

The very young are the most at risk - one of the only infections a child can pick up within the first 6 weeks of life - preventable through vaccination

Characterised by a whopping sound

Historically, 30 years ago was very common in children

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20
Q

How do we vaccinate against whopping cough in young babies

A

Babies younger than 6 weeks can get whooping cough -> for most other diseases the mothers antibodies still offer protection up until week 8 which is when first vaccinations are carried out

Because of this we offer a vaccine to pregnant mothers this way their immunity is passed onto baby

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21
Q

What has been the results of the whopping cough vaccine?

A

Crumlin was set up as the reference lab since it was traditionally a condition that only really affected young children

Since vaccination introduced whopping cough is not only found to affect adults with waining immunity

22
Q

What are the different stages of whopping cough?
(3)

A

Catarrhal stage: mild symptoms e.g. low grade fever and runny nose for 1 to 2 weeks

Paroxysmal stage: coughing stage, bursts of rapid cough accompanied by high pitch whoop noise, contagious for 1 to 6 weeks

Convalescent stage: gradual recover, coughs less frequet, 2 to 3 weeks

23
Q

Talk about the aetiology of whopping cough
(4)

A

Bordetella Pertusis main agent
Small aerobic gram negative coccobacillus
Bacteria attach to cilia of hosts respiratory cells
Produces toxins 1-5 which paralyze the cilia

24
Q

Comment on the epidemiology of whopping cough

A

Vaccination significantly reduced morbidity and mortality
Disease resurgence in highly vaccinated populations in adults
200 adult cases in 2017

25
Q

What are the four reasons for B.pertussis resurgence?

A

Improved diagnosis
Increased awareness
Waning immunity
Adaptation of the causative agent of pertussis

26
Q

How do we ID Bordetella Purtussis in the lab?
(4)

A

Nasal swab on charcoal blood agar with cefalexin incubated for 7 days

Can also be detected in blood culture

Charcoal based transport medium must be used and refrigerated if any delay

Culture methods, PCR methods, serological methods

27
Q

How would you confirm the ID of Bordetella pertussis
(3)

A

Small aerobic gram negative coccobacilli
Grey pearly colonies on charcoal medium
Should not grow on chocolate agar

28
Q

What are the pros and cons of using charcoal media for B. pertussis?

A

Pros: specificity excellent and cheap

Cons: low sensitivity (20-40%), takes 7 days, availability of good quality media/often fails qc checks

29
Q

What molecular methods are available for the ID of B. pertussis?

A

Real Time PCR
Biofire Filmarray respiratory 2.1 plus pnael

30
Q

What are the gene targers for Bordetella PCR?

A

B. pertussis insertion sequence IS481
B. parapertussis insertion sequence IS1001 -> the toxin promoter region

31
Q

How does PCR methods compare to culutre methods of detecting Bordetella

A

Real time PCR is 91% more effective at Identifing B. pertussis than culture

32
Q

What is the serological method of detection Bordetella, what sample is required?
(3)

A

An ELISA based method -> indirectly measures specific antiobdies against B. pertussis antigens

Test measures anti-pertussis toxin (PT) IgG in serum or oral fluids

Dual sampling during the acute and convalescent stage, at least three weeks apart is preferred

33
Q

What are the two kinds of URT air space infections?

A

Sinus infections

Middle ear infections

34
Q

What is a sinus infection?
(3)

A

An acute inflammatory condition of one or more of the paranasal sinuses

Secondary infection to an infection of one of the other respiratory sites -> most commonly the common cold

Last up to 4 weeks

35
Q

Write a note on the aetiology of sinusitis
(3)

A

Most commonly caused by the common cold i.e. rhinovirus

Can also be bacterial

Chronic sinusitis that lasts for 12+ weeks is usually due to a mixed infection of both aerobic and anaerobic organisms

36
Q

What bacteria are responsible for bacterial sinusitis?

A

S. pneumoniae (20-35%)
H. influenzae (6-26%)
M. catarrhalis (2-10%)

37
Q

What sequela are associated with bacterial sinusitis?

A

Meningitis
Brain abscesses

38
Q

Give an example of a case of chronic sinusitis

A

A microbiologist got chronic sinusitis from sniffing too many strep pneumo plates

39
Q

How are sinusitis infections investigated in the lab?

A

Usually get sinus/nasal washings/wash-outs
put up on blood and chocolate for 40-48 hours

Put up anaerobic agar e.g. neomycin FAA + metronidazole if query chronic infection for 5-7days for fuso or prevotella

Sabourad agar can also be put up if query fungus

40
Q

What is otitis externa?
(3)

A

Infection of the external ear canal

Causes irritation and pain in outer ear

External canal has similar flora to skin

41
Q

Talk about the aetiology of otitis externa
(list the 7 organism seen to cause otitis externa)

A

Most commonly caused by S. aureus and Gram negatives such as Pseudomonas aeruginosa (swimmers ear) and proteus species which favour a moist environment

Less common organisms include group A, C/G streps, anaerobes, enterobacteriacea and fungi

42
Q

What is otitis media?
(2)

A

Infection of the middle ear cavity

Build-up of pressure in the middle ear cavity that leads to pain and may lead to rupture of the ear drum

43
Q

Talk about the aetiology of otitis media
(3)

A

Mild forms are caused by rhinovirus and coronaviuses

Bacterial otitis is less common but more severe

Throat flora or pathogens spread to media through auditory tubes

44
Q

What four organisms are the most common causes of bacterial otitis media?

A

Strep pneumoniae (25-50%)
Haemophilus influenzae (5-10% type b, rest are NT)
Beta-lactamase producing Moraxella Catarrhalis (15-30%)
S. pyogenes 3-30%

45
Q

What are the sequela of otitis media?
(2)

A

Infection may spread to the mastoid air sinus and cause mastaiditis

From here it can spread to the cranial cavity and cause meningitis

46
Q

How would you investigate otitis

A

Blood for strep (+optochin) and moraxella
Chocolate for Hib
Neomycin FAA + mtz anaerobically for anaerobes and BHS (S. pyogenes)
MacConkey for enterobac and pseudos
Sabouraud for fungi

47
Q

How would you investigate otitis

A

Blood for strep (+optochin) and moraxella
Chocolate for Hib
Neomycin FAA + mtz anaerobically for anaerobes and BHS (S. pyogenes)
MacConkey for enterobac and pseudos
Sabouraud for fungi

48
Q

How would you confirm ID of S.pneumo
(11)

A

Gram positive diplococci
Alpha haemolysis on blood
Mucoid colonies or draught man colonies
Susceptible to optcohin
Bile Aesculin soluble
Commercial latex agglutination kit
Urinary streptococcal antigen kit
Capsular serotyping
Serology
PCR
Quelling reaction???

49
Q

How would confirm ID of M. catarrhalis in the lab

A

Gram negative diplococci that resist decolorisation
Hockey puck
Oxidase positive
DNase and Tributyin positive
Taxo disc (fail to ferment glucose, maltose, sucrose and lactose)
Catarrhalis disc test (produce a butyrate esterase enzyme)
PCR
copB outer membrane protein gene

50
Q

How would you confirm ID of a P. aeruginosa in the lab?

A

Gram negative bacilli
Oxidase positive
Glucose/Lactose non-fermenting (yellow on Mac)
Strict aerobe with growth temp range between 5 and 42 degrees -> wont grow at 4
Grows on most agars
Metallic sheen on BA
Sweet odour
B-haemolysis
Fluoresecent blue-green pigment on PA seletive agar due to pyocyanin and pyoverdin

4.1 Medical Microbiology (30 decks)

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